Chapter 3 · Discrimination · Case 7

Double chamber and branch discrimination V = A

Patient and episode

Patient

  • Simulator-generated atrial tachycardia trace on a Gallant dual-chamber defibrillator

Summary

  • VT2 in the V=A branch Both discriminants (morphology and onset of arrhythmia) are consistent with VT
  • SVT in the V=A branch Both discriminants (morphology and onset of arrhythmia) are consistent with SVT
  • SVT in the V=A branch Both discriminants (morphology and onset of arrhythmia) are consistent with SVT

The recording

Tap a number on the trace, or an entry in the list below

Episode 1

Abbott ICD electrogram, segment 1 of 3 — Double chamber and branch discrimination V = A
Abbott ICD electrogram, segment 2 of 3 — Double chamber and branch discrimination V = A
Abbott ICD electrogram, segment 3 of 3 — Double chamber and branch discrimination V = A
  1. Atrial detection and ventricular sensing
  2. onset of wide QRS, regular, monomorphic tachycardia with 1:1 atrioventricular conduction; the first rapid cycle is ventricular
  3. VT2 counter completed; effective burst
  4. Effective burst and diagnosis of end of episode

Episode 2

Abbott ICD electrogram, segment 1 of 5 — Double chamber and branch discrimination V = A
Abbott ICD electrogram, segment 2 of 5 — Double chamber and branch discrimination V = A
Abbott ICD electrogram, segment 3 of 5 — Double chamber and branch discrimination V = A
Abbott ICD electrogram, segment 4 of 5 — Double chamber and branch discrimination V = A
Abbott ICD electrogram, segment 5 of 5 — Double chamber and branch discrimination V = A
  1. Atrial detection and ventricular sensing
  2. acceleration of tachycardia with cycles classified as T1; most ventricular cycles have a correlation percentage greater than the programmed threshold
  3. after 3 cycles classified as T1, switches to episode mode (VVI), atrial markers are no longer displayed on the trace
  4. VT1 counter completed; diagnosis of SVT
  5. after 6 cycles classified as T1, SVT redetection
  6. acceleration of tachycardia with cycles classified as T2; confirmation of the diagnosis of SVT
  7. slowing in the VT1 zone
  8. slowing and diagnosis of end of episode

Episode 3

Abbott ICD electrogram, segment 1 of 4 — Double chamber and branch discrimination V = A
Abbott ICD electrogram, segment 2 of 4 — Double chamber and branch discrimination V = A
Abbott ICD electrogram, segment 3 of 4 — Double chamber and branch discrimination V = A
Abbott ICD electrogram, segment 4 of 4 — Double chamber and branch discrimination V = A
  1. Atrial detection and ventricular sensing
  2. starting on an atrial extrasystole of a 1/1 tachycardia
  3. cycles classified as T1; most ventricular cycles have a correlation percentage greater than the programmed threshold
  4. after 3 cycles classified as T1, switches to episode mode (VVI), atrial markers are no longer displayed on the trace
  5. VT1 counter completed; diagnosis of SVT
  6. after 6 cycles classified as T1, VTS redetection
  7. spontaneous reduction on a ventricular complex
  8. end-of-episode diagnosis

From the interrogation

Double chamber and branch discrimination V = A
Double chamber and branch discrimination V = A
Double chamber and branch discrimination V = A
Double chamber and branch discrimination V = A

Points to remember

  • In the presence of 1/1 tachycardia, various diagnoses are possible (VT with retrograde conduction, sinus tachycardia, 1/1 atrial tachycardia, junctional tachycardia).
  • In the V=A branch, two discriminants are used: morphology and onset of arrhythmia; these two criteria function in the same way as described for single-chamber discrimination; they may or may not be associated: “One of” or “All” criteria; on recent platforms, the initial cavity criterion has replaced abrupt onset as the nominal criterion.
  • It is a different algorithm that also analyzes the sudden onset, but in a different way than the old sudden onset alone present in the single chamber; in fact, the analysis of the onset alone (sudden or gradual) allowed for the discrimination of sinus tachycardias but not atrial tachycardias; the analysis of the initial cavity allows this limitation to be addressed.
  • The arrhythmia onset/initial cavity discriminant analyzes both the atrial and ventricular channels, assessing whether there was a sudden onset in both cavities and whether the arrhythmia began in the atrium or ventricle.
  • if the onset of arrhythmia is considered gradual, the discriminant favors SVT; if the onset is considered sudden and the initial cavity is the atrium, the discriminant favors SVT; if the onset is considered sudden and the initial cavity is the ventricle, the discriminant favors VT
  • the first tracing corresponds to VT with 1:1 retrograde conduction; the tachycardia starts on a premature ventricular complex; the two discriminants (morphology and onset of arrhythmia) favor VT; indeed, the appearance of the ventriculograms is clearly different in tachycardia compared to sinus rhythm, and the onset of tachycardia is abrupt with a first premature ventricular complex
  • the second trace corresponds to a well-defined episode of sinus tachycardia; the two discriminating factors (morphology and onset of arrhythmia) are consistent with SVT; the gradual acceleration followed by deceleration are consistent with a diagnosis of sinus tachycardia
  • The third trace corresponds to a clearly distinguished episode of atrial tachycardia; the two discriminating factors (morphology and onset of arrhythmia) point to SVT; indeed,the appearance of the ventriculograms is clearly similar in tachycardia compared to sinus rhythm, the onset of tachycardia is sudden with a first premature atrial complex; the tachycardia stops spontaneously on a ventricle

Practice out loud

Just describe the tracing. What do you think is going on? Describing the numbers can help.

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From Implantable Cardioverter Defibrillator — clinical cases based on tracings by P. Bordachar, M. Strik, A. Thiyagarajah, S. Ploux. Published by Cardiocases. Every numbered marker on a recording is explained in the list beneath it; tap a marker on the trace or an entry in the list.